Is The Odor of Cannabis Sufficient to Justify a Search of a Vehicle?

Is the odor of cannabis sufficient to detain an individual and search their person or vehicle?  The changing landscape of cannabis and hemp laws across the nation and here in Pennsylvania may put a stake through the heart of this “tried and true” law enforcement technique.

Under current Pennsylvania law, the “plain smell” doctrine can establish reasonable suspicion or probable cause to detain an individual and conduct a vehicle search.  As recently as 2018 the Pennsylvania Supreme Court in In the Interest of A.A. reaffirmed that “the odor of marijuana alone, particularly in a moving vehicle, is sufficient to support at least reasonable suspicion, if not the more stringent requirement of probable cause.”  The arrest in A.A. predated Pennsylvania’s medical cannabis law.

Does the “plain smell” test survive in the age of legal medical cannabis and legal hemp in Pennsylvania?  

Until recently cannabis sativa l, aka “marijuana”, was illegal in all of its forms and derivatives.  The past twenty years have witnessed a seismic shift in cannabis prohibition. Thirty-three states have legalized some form of medical cannabis.  Eleven states and the District of Columbia have also legalized all “adult use”. Pennsylvania’s medical cannabis program has registered over 200,000 patients and has distributed millions of products since February, 2017, when the first dispensaries opened their doors.  “Dry leaf” or “flower” was added as a legal medical cannabis product in May, 2018, and was available in dispensaries in August, 2018.  

In December of last year the Farm Bill was signed in to law.  The Farm Bill legalizes the cultivation of cannabis plants with less than .3% THC, also known as “industrial hemp.”  It also legalizes the commercial application of hemp products, from textiles to food products and health supplements.  Cannabinoids extracted from hemp, such as cannabidiol (CBD), are legal pending regulations from the Department of Agriculture and the Food & Drug Administration.

Law enforcement, cannabis consumers and even some non-consumers can recognize the distinctive odor of either “fresh” cannabis or burned cannabis.  What is it that gives cannabis this distinctive odor? Is it the presence of the psychoactive chemical tetrahydrocannabinol (THC)? Actually, no, as THC has no detectable odor.  That distinctive smell comes from “terpenes”.  According to Jason Lupoi, PhD, Editor-in-Chief of Terpenes and Testing Magazine: 

“(t)erpenes are volatile, fragrant molecules in a myriad of plants, and comprise the bulk of many plants’ essential oils. Because of their volatility, you can often smell their essence at ambient conditions, such as when smelling plants, such as a flower, a forest, an orange, or a cannabis plant. Over 200 terpenes have been identified in cannabis (Russo, British Journal of Pharmacology (2011), Volume 163: 1344–1364, and references therein). Due to the volatility of these molecules, they are responsible for the trademark aromas of cannabis cultivars, whereas cannabinoids are not (Russo, 2011) . . . Chemical characterization of the cannabinoids and terpenes have routinely shown that one cannot differentiate cannabis cultivars using cannabinoid content, since most cultivars have statistically similar levels of THCA (Hazekamp & Fischedick, Drug Test Anal. 2012 Jul-Aug;4(7-8):660-7; Orser et al., Nat Prod Chem Res 2018, 6:1) . . . What has enabled differentiation of the plants are the terpenes, which do vary from cultivar-to-cultivar, hence the different aromas.”

Terpenes are found in cannabis with high THC content and hemp with a THC content of .3% or below.  What this means is that the “odor” detected by the officer (or the K9, which is trained to detect a specific terpene) may come from “marijuana” or it may come from legal hemp flower.

Well, ok – the officer should be entitled to at least detain the individual until the officer can determine whether the odor if from a legal hemp product or legal medical marijuana product, correct?  Not so fast. A recent Pennsylvania Supreme Court decision may signal the end of the “plain smell” doctrine relative to the odor of cannabis.  

In Commonwealth v. Hicks, the Supreme Court of Pennsylvania addressed the issue of whether a law enforcement officer had probable cause to detain an individual observed carrying a concealed firearm.  In Hicks the defendant was observed via a store surveillance camera to have a concealed firearm.  Police viewed the footage and then detained the individual. The defendant possessed a valid PA concealed carry permit, but was found in possession of cannabis and ultimately charged with a DUI.  

Justice Wecht, writing for the majority, said “Under Pennsylvania law, there can be no doubt that a properly licensed individual who carries a concealed firearm in public engages in lawful conduct. Indeed, millions of people lawfully engage in this conduct on a daily basis, both within this Commonwealth and across the nation.”  Justice Wecht continued:

“We find no justification for the notion that a police officer may infer criminal activity merely from an individual’s possession of a concealed firearm in public. As set forth, above, it is not a criminal offense for a license holder, such as Hicks, to carry a concealed firearm in public.14 Although the carrying of a concealed firearm is unlawful for a person statutorily prohibited from firearm ownership or for a person not licensed to do so, see 18 Pa.C.S. §§ 6105-06, there is no way to ascertain an individual’s licensing status, or status as a prohibited person, merely by his outward appearance. As a matter of law and common sense, a police officer observing an unknown individual can no more identify whether that individual has a license in his wallet than discern whether he is a criminal. Unless a police officer has prior knowledge that a specific individual is not permitted to carry a concealed firearm, and absent articulable facts supporting reasonable suspicion that a firearm is being used or intended to be used in a criminal manner, there simply is no justification for the conclusion that the mere possession of a firearm, where it lawfully may be carried, is alone suggestive of criminal activity.”

Thus, because carrying a concealed firearm is lawfully permitted in Pennsylvania, merely observing a concealed firearm cannot provide a legal basis to detain an individual.

Recently, a trial court in Lehigh County suppressed the search of a motor vehicle due to the odor of cannabis.  In Commonwealth v. Barr a Lehigh County Court of Common Pleas Judge suppressed the search of a motor vehicle where the police officer detected an odor of marijuana, using same to justify the warrantless search of the vehicle.  The defense presented an expert witness who testified that legal medical cannabis and illegal “street” cannabis had the same chemical profile and were indistinguishable. The Court noted that once the defendant showed his medical cannabis patient identification the officer had no legal basis to believe the odor was from illegal “street” cannabis versus legal cannabis from a licensed medical cannabis dispensary.  The Court suppressed the search of the motor vehicle.

While Barr is not precedential, it, along with Hicks, provides guidance relative to how Courts may rule on suppression motions when the search is based solely on the odor of cannabis.  A police officer cannot distinguish between legal medical cannabis and illegal “street” cannabis based on smell. Nor can an officer distinguish cannabis with THC from hemp with trace amounts of THC.  Applying the holding in Hicks, there is simply no way for an officer to distinguish legal medical cannabis or legal hemp from illegal street cannabis.  To paraphrase Justice Wecht’s quote 

“Under Pennsylvania law, there can be no doubt that a properly licensed individual who possess medical cannabis engages in lawful conduct. Indeed, millions of people lawfully engage in this conduct on a daily basis, both within this Commonwealth and across the nation.” 

Because both medical cannabis and hemp are legal in PA Hicks tells us that, without more, merely smelling an odor of cannabis should not create either reasonable suspicion or probable cause.  I, for one, will be filing Motions to Suppress whenever stop or search is based solely upon the odor of cannabis.

If you have questions about your rights as a medical cannabis or “adult use” consumer please do not hesitate to contact me at 412.454.5582 or 



  • Kris Kelly says:

    Can you tell me if the Pa Supreme Court has recently ruled that the odor of marijuana coming from a vehicle is Not probable cause to search a vehicle? I’m in a discussion concerning this matter.

    • Patrick Nightingale says:

      Apologies for the delayed reply – this message was buried in spam. The Superior Court held in Com. v. Barr that the odor of cannabis is no longer per se probable cause. That means an affiant requires something in addition to the odor – an admission, other corroborating evidence, etc.

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